1. Field of the Invention
The present invention relates to biphenyl derivatives. More particularly, it relates to biphenyl derivatives which exhibit dopamine 2 receptor antagonism and/or serotonin 2 receptor antagonism and which are clinically useful as therapeutic and ameliorative agents for mental disorders such as cerebrovascular disorder, aggressive behavior due to senile dementia, mental excitation, poriomania, delirium, hallucination, hyperkinesia, schizophrenia, emotional disturbance, depression, neurosis, psychophysiologic disorder and anxiety neurosis.
2. Description of the Related Art
Mental disorders such as cerebrovascular disorder and dementia are frequently found in the aged, which becomes a significant problem with the approach of an aging society. In many cases, these diseases are accompanied with mental and/or behavior disorders which specifically appear as delirium, hallucination, hyperkinesia, poriomania, mental excitation or other sign or symptom. These signs and symptoms not only have an adverse effect on a patient himself, but also necessitate everyday care, imposing a heavy burden on the people around the patient. Under these circumstances, the development of a highly clinically useful medicine which can treat the above mental disorders medically has been expected not only by patients and their families, but also socially.
Only Tiapride is now authorized as a therapeutic and ameliorative agent for the above diseases, and Haloperidol which is an antischizophrenic drug is also used, though the diseases are not included in the indications for which the drug is efficacious.
As novel compounds having an antipsychotic activity, benzisothiazole derivatives and benzisoxazole derivatives are disclosed in European Patent Publication-A No. 196132, and pyridine derivatives are disclosed in U.S. Pat. No. 5,021,421.
Tiapride and haloperidol are medicines exhibiting dopamine 2 (D.sub.2) receptor antagonism. A medicine of this type has a problem of causing extrapyramidal syndrome including dystonia (hypermyotonia or muscle hypotonia), hypokinesis (akinesis), hyperkinesia (abnormal movement) and so forth as an adverse reaction, though the medicine is clinically efficacious.
Risperidone which is a representative example of the benzisoxazole derivative disclosed in the above European Patent Publication-A No. 196132 is authorized as an antischizophrenic drug in the United States, the United Kingdom and Canada. However, this drug is problematic in that blood-pressure drop occurs as an adverse reaction owing to the high .alpha..sub.1 blocking activity of the drug and that the QT.sub.C interval in electro-cardiogram is lengthened to induce arrhythmia, being undesirable particularly when administered to a patient of advanced age.
The pyridine derivative disclosed in the above U.S. Pat. No. 5,021,421 also exhibits potent dopamine 2 receptor antagonism and is therefore feared to cause extrapyramidal syndrome like Tiapride or Haloperidol. Further, the pyridine derivative has not been used clinically as yet, so that its safeness in prolonged application is not apparent.
As described above, there has not been found any therapeutic and ameliorative agent for mental disorders such as cerebrovascular disorder, aggressive behavior due to senile dementia, mental excitation, poriomania, delirium, hallucination, hyperkinesia, schizophrenia, emotional disturbance, depression, neurosis, psychophysiologic disorder and anxiety neurosis, which has high clinical usefulness and is excellent in safeness.